US1793428A - Telescope with porro prism system - Google Patents

Description

Feb. 17, 1931. AIKONIG 1,793,428

' TELESCOPE WITH PORRO PRISM SYSTEM Filed Jan. 11, 1929 Fig.4

Patented Feb. 17, 1931 UNITED. STA ES PATENT OFFICE ALBERT KGNIG, OF JENA, GERMANY, ASSIGNOR TO THE FIRM CARL ZEISS, OF JEITA, I l GERMANY TELESCOPE WITH PORRO PRISM SYSTEM Application fi1ed.January 11, 1929, Serial No. 331,799, and in Germany January 14, 1928.

The invention relates to a telescope with a relation of the diameter of the objective to the diameter of the eyepiece diaphragm between 0.8 and 3.2, with a Porro prism system 5 consisting of two right-angled prisms.

In order to obtain for such telescope and especially for a double telescope composed of two such telescopes a construction as compact as possible, the prism system, according to the invention, is designed in such a way that the sum of the absolute values of the two parallel displacements of the axial ray will be smallenthanthree and one half times the value of thequotient of the product and the sum of the -tw'ocliameters.

Let -V designate the dimension of the prism belonging to the objective of the telescope in a, plane which is inclined by 12 to the planecontaining the axial ray immedi- 2t ately before and immediately after the first reflection and the axis of the entering ray,

the dimension counting from this axis, and further let V designate the dimension of the prism belonging to'the eyepiece of the telescope in a plane which is inclined by 12 to the plane containing the axial ray immediately before and immediately after the lastreflection and the axis of the emerging ray, the dimension counting from this axis. Then it is advisable to take .care that the sum (V -F1 of the absolute values of these two dimensions will be smaller than four and one half times the aforesaid quotient. F urther it isappropriate to see to it that each of the said two dimensions will be smaller than 1.3 times the value of the appertaining displacement of the axial ray.

The annexed drawing shows a prism system in correspondence with the present invention. Fig. 1 represents across section of the system whereas Fig. 2 illustrates the prism which is to be considered as, belonging to the objective of the respective telescope, and Fig. 3 shows in side elevation the prism, to be considered as belonging to the eyepiece.

The prism system represented by the drawing is designed for a telescope having the following values:

Diameter of objective, O=72 mm.

' angled prisms a and b, of which a is to be considered as belonging to the objective and b to the eyepiece of the telescope. The cross section of the path of the rays is D when entering, D when emerging and B, when passing on from one prism to 'the other, whereby D is smaller than D and smaller than D and equal to the said quotient y. The axis of the entering rays is denominated R-R, the axis of the emerging rays TT. The displacements of the rays RW and WT in the objective prism a and in the prism of the eye iece b are designated P and P The sum 0 the absolute values of P and P is equal to 2.83 y. The greatest dimension of the objective prism (1, taken from the axis of the entering my RR in a'plane E which is inclined. by 12 to the plane E con-, taining the axial ray in the objective prism a, and thereby contains the axis of the entering ray RR is BS V =1.246 P whereas the greatest dimension of the ocular prism 6, taken from the axis of the emerging ra TT in a plane E which is inclined-by 12 to the plane E, containing the axial ray in the prism b of the eyepiece and thereby contains the axis of the emerging ray TT, is TU V 1.282 P The sum of the absolute values of V and V therefore, only amounts to 3.57 y. The form of the side planes bordering the prisms, as represented in the drawing, is of no importance to the invention.

I claim: A

1. A telescope where the relation of diameter of objective to diameter of eyepiece diaphragm is between 0.8 and 3.2, containing a Porro prism system consisting of two right-angled prisms ofsuch dimensions that the sum of the two parallel-displacements which the axial ray is given in the prisms will be smaller than three and one half times the 100 I value'iof sum of the said-twolfdiametersr 5.4;? a

- of .the absolute values of, the? o v v v thep'rism belonging to the objective-in a fore and immediately after thefirst reflectionfi a and thefaxis of the entering ray,'and -of fthe I dimension of the prism belonging to the-eye- I immediately before and immediately after the last reflection and the axis of'the emer ing ray, being-smaller than four and one ha f v 2;" A telesc" pe where the --rela .tion-.-of di- 1 ameter off objectiveto diameter oi eyepiece diaphragm is -between '-0 .8-andi-3r2 contain-i inga Porro prism system consisting offltwo 1 v .i

right-angled prismsoffsuch dimensions that the sum of the two parallel-displacements f.

which the axial ray is given' in the prisms vvill i be smaller'than three and'one'half times the 3 value of the quotient .oftheproduct and' the sum 1 of the said twodiameters, anewespm plane which i's 'inclinedby 12 tothat-1pla which contains the axial ray immediately;

pie'cein a' plane which is inclined'by 12 tothat plane which contains'the axial ray times the value of the said quotient.

'3. A-telescope where. the relation of di-- ameter of. objective to diameter of eyepiece diaphragm is between 0.8 and 3.2, Contain- I ing a Porro prism system consisting of tworight-angled prisms of such dimensions that the sum of. the two parallel-displacements which the axial ray is given in the prisms will be smaller than three and one half times the value of the quotient of the product and the sum of the said two diameters, and the v sumof the absolute values of the dimension of the prism belonging to the objective in a plane which is inclined by 12 to that plane which contains the axial rayimmediately before and immediately after the first reflection and the axis of the entering ray, v 1

and of the dimension of the rism belonging to the eyepiece ina plane w ich is inclined by 12 to that plane which contains the axial ray immediately before and immediately after the last reflection and the axisof the emerging ray, being smaller than four and one half times the value of the said quotient, and each of. the said two dimensions being smaller than 1.3 times the value of the appertaining displacements'of the axial ray.

ALBERT KONIG.

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